Tunable Emission in Heteroepitaxial Ln‐SURMOFs

Chen, Dong‐Hui; Haldar, Ritesh; Neumeier, B. Lilli; Fu, Zhaoming; Feldmann, Claus; Wöll, Christof; Redel, Engelbert

doi:10.1002/adfm.201903086

Cited by 43 publications

(44 citation statements)

References 39 publications

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“…[174] Particularly interesting, with regard to realizing mixed-metal MOFs, are lanthanide-based SURMOFs, since the very similar coordination chemistry of these metal ions allows switching between the different elements without pronounced changes of the MOF structure. [175] Figure 11. Layer-by-layer growth of a HKUST-I SURMOF on a quartzcrystal microbalance (QCM) crystal.…”

Section: Methodsmentioning

confidence: 99%

Proximity Effect in Crystalline Framework Materials: Stacking‐Induced Functionality in MOFs and COFs

Kuc

Springer

Batra

et al. 2020

Adv Funct Materials

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Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) consist of molecular building blocks being stitched together by strong bonds. They are well known for their porosity, large surface area, and related properties. The electronic properties of most MOFs and COFs are the superposition of those of their constituting building blocks. If crystalline, however, solid-state phenomena can be observed, such as electrical conductivity, substantial dispersion of electronic bands, broadened absorption bands, formation of excimer states, mobile charge carriers, and indirect band gaps. These effects emerge often by the proximity effect caused by van der Waals interactions between stacked aromatic building blocks. Herein, it is shown how functionality is imposed by this proximity effect, that is, by stacking aromatic molecules in such a way that extraordinary properties emerge in MOFs and COFs. After discussing the proximity effect in graphene-related materials, its importance for layered COFs and MOFs is shown. For MOFs with well-defined structure, the stacks of aromatic building blocks can be controlled via varying MOF topology, lattice constant, and by attaching steric control units. Finally, an overview of theoretical methods to predict and analyze these effects is given, before the layer-by-layer growth technique for well-ordered surface-mounted MOFs is summarized.

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Section: Methodsmentioning

confidence: 99%

Proximity Effect in Crystalline Framework Materials: Stacking‐Induced Functionality in MOFs and COFs

Kuc

Springer

Batra

et al. 2020

Adv Funct Materials

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“…Accordingly, one would expect that the structural parameters of a Ln-based MOF would vary only a little when using a different lanthanide. Redel and coworkers recently demonstrated that, indeed, this approach enables the heteroepitaxy of Ln-based SURMOFs to be realized in a straightforward fashion [54].…”

Section: Heteroepitaxial Mof-on-mof Thin Films: Photophysical Propertiesmentioning

confidence: 99%

Hierarchical assemblies of molecular frameworks—MOF-on-MOF epitaxial heterostructures

Haldar

Wöll

2020

Nano Res.

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Functional, porous metal-organic frameworks (MOFs) have attracted much attention as a very flexible class of crystalline, porous materials. For more advanced applications that exploit photophysical properties, the fabrication of hierarchical assemblies, including the creation of MOF/MOF heterointerfaces, is important. For the manufacturing of superstructures with length scales well beyond that of the MOF pore size, layer-by-layer (lbl) methods are particularly attractive. These allow the isoreticular approach to be extended to superstructures with micrometer length scales, a range that is not accessible using conventional MOF design. The lbl approach further substantially extends the compositional diversity in MOFs. At the same time, the favorable elastic properties of MOFs allow for heteroepitaxial growth, even in the case of lattice misfits as large as 20%. While the MOF-on-MOF approach to designing multicomponent superstructures with synergistic multifunctionality can also be realized with sophisticated solvothermal synthesis schemes, the lbl (or liquid-phase epitaxy) approach carries substantial advantages, in particular when it comes to the integration of such MOF superstructures into optical or electronic devices. While the structure vertical to the substrate can be adjusted using the lbl method, photolithographic methods can be used for lateral structuring. In this review, we will discuss the lbl liquid-phase epitaxy approach to growing surface-anchored MOF thins films (SURMOFs) as well as other relevant one-pot synthesis methods for constructing such hierarchically designed structures and their emerging applications.

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“…[176] Particularly interesting, with regard to realizing mixed-metal MOFs, are lanthanide-based SURMOFs, since the very similar coordination chemistry of these metal ions allows switching between the different elements without pronounced changes of the MOF structure. [177] Crystalline framework materials offer an additional means for functionality design: controlled van-der-Waals stacks of aromatic building blocks are subject to the proximity effect and raise phenomena such as wide absorption bands, mobile charge carriers, or indirect band gaps. Such stacks are present in layered MOFs and COFs, and can be created via steric control in 3D frameworks.…”

Section: Dftbmentioning

confidence: 99%

Proximity Effect in Crystalline Framework Materials: Stacking-Induced Functionality in MOFs and COFs

Kuc¹,

Springer²,

Batra³

et al. 2019

Preprint

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<div>Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) consist of molecular building blocks being stitched together by strong bonds. They are well known for their porosity, large surface area, and related properties. The electronic properties of most MOFs and COFs are the superposition of those of their constituting building blocks. If crystalline, however, solid-state phenomena can be observed, such as electrical conductivity, substantial dispersion of electronic bands, broadened absorption bands, formation of excimer states, mobile charge carriers, and indirect band gaps. These effects emerge often by the proximity effect caused by the van-der-Waals interactions between stacked aromatic building blocks. This Progress Report shows how functionality is imposed by this proximity effect, that is, by stacking aromatic molecules in such a way that extraordinary electronic and optoelectronic properties emerge in MOFs and COFs. After discussing the proximity effect in graphene-related materials, its importance for layered COFs and MOFs is shown. For MOFs with well-defined structure, the stacks of aromatic building blocks can be controlled via varying MOF topology, lattice constant, and by attaching steric control units. Finally, an overview of theoretical methods to predict and analyze these effects is given, before the layer-by-layer growth technique for well-ordered surface-mounted MOFs is summarized.</div>

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Tunable Emission in Heteroepitaxial Ln‐SURMOFs

Cited by 43 publications

References 39 publications

Proximity Effect in Crystalline Framework Materials: Stacking‐Induced Functionality in MOFs and COFs

Proximity Effect in Crystalline Framework Materials: Stacking‐Induced Functionality in MOFs and COFs

Hierarchical assemblies of molecular frameworks—MOF-on-MOF epitaxial heterostructures

Proximity Effect in Crystalline Framework Materials: Stacking-Induced Functionality in MOFs and COFs

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